


Bone: Anatomy

by shadowarchives



Series: Bone, Flesh and Blood (untold chapters of the undertale trilogy) [1]
Category: Undertale (Video Game)
Genre: May contain disturbing scene descriptions, Prologue to Gaster, Sans is the main character however, Untold chapter of the undertale trilogy
Language: English
Status: Completed
Published: 2017-12-01
Updated: 2017-12-17
Packaged: 2019-02-09 08:32:32
Rating: Mature
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 15
Words: 9,445
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12884028
Author URL: https://archiveofourown.org/users/shadowarchives/pseuds/shadowarchives





	1. The truth

Throughout the time that the human known as Frisk knew her friends Papyrus and Sans, she always had many questions about their ethics. One thing she never came to realize was why Sans stayed in his room most of the time, or why his Right hand was always in his pocket, or why only his left eye lit up in flames during his attacks.

One day however she was Determined to get the answer as Sans was sleeping on the couch in his home, taking a nap whilst Frisk did some homework for school. She carefully sneaked downstairs to have a look, she almost got caught in the act as the bottom stair creaked harshly round the house. But Sans just rolled a little, still asleep. Frisk tip-toed over to the couch and lightly pulled Sans' hand out of his jacket... What she saw was not to be expected.

"You saw WHAT!!" Sans says as they chat over a quick lunch. Frisk didn't expect Sans to speak like this when she politely asked why Sans had four scars digging into his hand, just where the knuckles would be. 

"I'm sorry Sans, i was just really concerned about the scars. I had no idea you would be concerned." Frisk says in a slightly panicked way.

"Jesus kid i know you were raised pretty poorly but do you have to know everything." Sans replies as he looks down at scars on his hand. He blinks his eyes shut. Blue flame appears to erupt from his eye as rubs his eye. He appears to be in pain, but not physically from the eye.

"Sans are you alright. Listen i know it wasn't my place to know what the scars were but what if Papyrus or Toriel or Asgore found out about this?" Frisk questions.

"Heheh, looks like they're actually one step ahead of you kid." Frisk looks confused, sans may be a joker but she couldn't tell if he was serious or messing with her. "What do you mean." Sans realized he probably shouldn't have said that but his mindset changes and says to Frisk. "Nothing, just a thought that crossed my mind... Listen i know i've told you before that i'm not good with promises or asking for promises, but. If i tell you what happened, you must promise me not to tell anyone else. Got it!"

Frisk nods in agreement "OK i understand." Sans sighs in slight relief and thinks of where to start. "Alright then well you know how i told you about that colleague i worked with back in the underground... Well me and him were doing a lot of experiments with the monster anatomy, and learnt how human souls could change how we act. One of the souls we worked on was a Dark blue soul and contained properties that most people would consider unnatural... It was used as a more defense soul, countering anything a monster would throw at it. But sometimes souls can be pushed to their limits. You've already seen that with Determination. But when a monster soul is pushed to it's limits. It evolves. Every so often a monster evolves into their next generation like humans... Even if it goes terribly wrong... What i'm trying to say is at the end of the day. It was Evolution that caused my colleague to die. And that evolution, was me..."

Sans released his held breath and prepared to explain to Frisk what happened a long time ago, before frisk was even in the underground... Before there was peace in the world...


	2. Sans Serif

Many years ago...

Sans opens his eyes, he is in a containment cell floating in liquid. The smells of chemicals and the sound of plastic and metal are sensed as the liquid is drained and the chamber opens. Sans steps out and walks around. He goes to the computer to analyze his results. Every piece of binary code and random segmentation is displayed on a computer screen as he studies the information on his anatomy.

Name: Sans  
Age: Undefined (maturity, teenager)  
Relation: W.D Gaster (Father) Papyrus (younger brother) Mother undefined  
Soul specification: None  
Powers: Bone daggers, Bone Swords, bone manipulation (structure based)

Soul information: refraction, all 7 soul aspects found  
Relaying data to current souls  
Light Blue: Positive mutation  
Purple: Positive mutation  
Blue: undefined mutation  
Data transfer complete, storing soul files  
Serifim structure analysed, creating chemical formula  
Process complete, preparing DNA extraction

A syringe is lowered next to the machine as Sans holds one arm out and extracts his blood and soul magic into the syringe

DNA collected, analysing...  
Chemical evolution complete. Creating Serifim now...  
Process complete

Another syringe is produced filled with a Navy blue liquid that Sans injects into his arm. All of the scars from his testing are healed and he puts his lab clothing on,  
He looks back at the laboratory extraction room and then at the scar on his arm.

("What on earth i was really doing in that lab, i had no idea. But Gaster needed his analysIS of our maturing anatomy so he could develop our powers... Y'see Serifim is a liquid that Myself and Gaster were developing to create an alternative to determination, it was made based on the analyzing we had done of our DNA when compared to other monsters. Serifim worked very much like determination, healing wounds, creating stronger attacks. But we were just on the tip of the Iceberg. We never knew that this liquid could turn us into Demons... And that it did.")


	3. Like father like son

Gaster looked up at the walls he had decorated in the lounge area of the lab. Portraits of monsters in the Great War are displayed as he drinks his coffee and makes notes.

He then goes to his computer to look at some scientific data when Sans walks in. He gives Gaster a data transfer that he collected from his DNA analysis.

“Still no development, the Blue soul is still undefined in mutation G”

Gaster let’s out a small groan as he reads over the data noticing the syringe scar on Sans arm. 

“Well I guess we’re at a stalemate Son, We’re the next jump in monster kind.” Gaster says as he gives a vague smile at his Son.

“What is Asgore gonna make of this, what will his concerns be to-“ but Gaster gets out of the chair and heads to the door “Asgores concerns are not involved with us, I wish you would have more faith in our work Sans... Anyways I’ll be in the house if you need me...”  
Gaster exits the room as Sans looks over the data again. 

“Always on the move.” He says in a reluctant way as he leaves the workplace and heads out of the laboratory.

He walks up the snow covered stairs from the lab and walks to the front of the house. Giving a polite wave to whoever he passes by, he arrives at grillbys and orders a drink. An argument appears to be emerging between two people.

“Of course it’s right to support the kings movements, so what if the souls are kept away from us”

“Well I think he’s up to no good”

“God you’re sounding like a human”

“Am not!”

“Hey!” Sans says interrupting them. “Leave him be, asgore decides what happens and you two can’t decide anything about it. Now Can I get you gentlemen anything?” 

The loud one retaliates and kicks Sans into a table preparing to badly hurt him.

“Yeah well you can give the satisfaction of kicking you in the teeth!” Grillby the bar owner sees the commotion and prepares to stop them both but Sans feels a reaction inside him from his anger and the monsters soul turns blue. Sans throws him up into the ceiling and then smashes him back down again. “Watch your tongue buddy.”

“Alright break it up you guys!” Grillby says as the two arguing monsters leave in fear and pain whilst some look on or leave as well. Sans walks back to the bar.

“Pricks, they don’t understand”

“Keep your attitude down Sans, don’t want to end up in the wrong side of the world”

“Trust me, I’m doing a pretty good job already. See ya later Grillby.” Sans says as he finishes his drink and throws it in the bin, smashing it with a bone, he heads back to the home wondering how he changed in that bar. How could he throw that monster into the ceiling, what was that Serifim doing to his abilities.


	4. Brothers

Sans walked through the doorway into his house which was far warmer than outside in the cold, he saw his brother up on the stairway and gave him a friendly wave.

"Brother you're back!" Papyrus says as he runs down the stairs and towards his brother, sans lifts him up in the air as the two of them chuckle to themselves. "Heheheh, how's it going pap." Sans puts him back down as papyrus smiles up at his idol. "I'm alright thanks, where have you been, father said you two were busy somewhere and i had to stay indoors." Sans knowing what his father would say about him telling Papyrus about their scientific tests, fakes out what he's been doing. "Eh, y'know i've uh, been at grillby's seeing what he's been up to." Papyrus chuckles "What, that's it. You are a lazy bones sometimes brother." Sans rubs his brothers head "Hey watch it you, heheheh. Laziness isn't the least of my problems. Anyways lets sit down and have a chat together."

("Papyrus, heheh. Well he was a lot younger back then, nowadays he towers over me but back then he was only a child. Heh, for a skeleton's age anyway. I could lift him up in the air swing him round like he was as light as a feather. But even when i stopped growing he just kept on getting taller. Me and him had our differences even back in the day. Just shows how our gene pools have manufactured us into what we are today.")

"Wow that's a great puzzle, heh if Undyne were here she would be impressed that a kid your age would be able to think of something like that." Sans says as he looks at Papyrus' drawing of a puzzle for humans to solve. "Thanks brother, do you think father would like it too." Sans chuckles "I'm sure he would bro... So what's the deal around snowdin, heard any news from your friends lately." Papyrus shakes his head "No, just the same old stuff that happens all the time.. Although i talked to monster kid the other day, and he seemed to talk about you a lot... Is something going on that he knows about." Sans frowns ("Why the hell is that kid getting involved") "Don't think so no... Hey listen can you do me a favor and finish this puzzle i've been working on. I've gotta talk to our father." Papyrus smiles "Sure no problem, see you later." 

As Sans walks round the stairs to a room where Gaster was working Papyrus calls him. "Brother! This puzzle is easy?!" Sans plays along "Really, i thought it was difficult, heheheh." Papyrus sarcastically rolls his eyes around as Sans enters the other room where his comedic tone turns serious as Gaster works on a computer.

"Hey G. I thought you said that the computer files were always up to date." Gaster looks round to see his eldest son looking sternly at him. "Of course they are Sans, no faults at all should be in the system." Sans doesn't look convinced. "Then would you care to explain why i can suddenly do this?!" Sans grabs a book from a shelf and throws it with his soul magic into a plant pot with nothing but Soil in it. The plant pot smashes and the soil spills all over the wooden table it's on covering a blueprint Gaster was working on. His Father turns around in shock to the plant pot and book, and then at his son. "What on earth?-" But before he can ask how Papyrus calls from the living room "Brother is everything alright in there?" Sans calls back "Yeah bro, we're good just accidentally spilled something."

"But how is this possible Sans, the Serifim formula isn't complete?" Sans turns back to his father. "Well it looks like you can tell your computer that the soul extraction was a success. Your formula is done professor." Gaster types into the computer Sans' new information and the computer resets to follow his calculations, Gaster stands up in half shock, half excitement and walks to the blueprints slamming his hands on the table and letting out a groan of relief.

A moments silence passes before he breaks the silence. "Well that's it then... We have our answer to determination..."


	5. Update to the system

Sans and Gaster make their way to the Power testing area of the laboratory. This wing of the lab was a sealed off corridor made to replicate the conditions of the underground as well as earth, so that monsters that would take on the humans would be able to practice power amplification as well as test new prototype powers.

"Now that we have a finished formula for Serifim we can-" "Analysed." Sans says interrupting Gaster mid sentence. "I've only analysed a finished formula, the truth is we don't know what exactly this formula can do a monster, or even if it's fully safe yet." Gaster looks at Sans with a sense of knowing "It's finished if i say it's finished Sans, we can start the testing now but as far as anyone else is concerned it is fully operational and ready for use." 

Gaster heads over to a containment chamber with a couple of holders for syringes he places them in but takes one filled with the formula and injects himself. Sans watches this whilst he works on the computer, setting up the magic connections to a new ability that he would soon use. "Be careful with that Professor, don't want to overdose on a single needle." Gaster looks up at Sans "I think it's right that we overdose, besides. It's our world to make choices isn't it? And with choices comes consequences." Gaster says as he uses a power very much like Sans' to create a hand a grab another syringe to put into the containment chambers holders. 

"Consequences aren't a laughing matter G." Gaster configures the holders whilst talking to Sans "And consequences should be known Sans. There will come a time where you must learn to live with your choices." Sans rolls his eyes as he gets back to work. "You wanna come and check real quick on how the prototype is going." Gaster turns round and obliges to Sans' gesture. "What's the details so far." Sans looks through the files on the new attack method. "Yeah it's looking good, almost ready to be used properly. But it will take a little more analyses of the soul data to get things ready, I'll have a look at the blue soul and see if we can figure something out..."

"Hey do you think the serifim will be able to trigger the Gaster blasters properly?" Sans hears a smash in the room and looks over to gaster. "What the hell G."   
Gaster looks down at Sans with a stern look on his face "we're not calling them that and you know it." Sans walks away from the computer heading to the soul containment room "I just thought it would be a catchy name. Besides, you're meant to be the one who's using them right. The one with a power that can "Break through the barrier..." Anyways let me know if you find anything useful." 

Sans heads round to the soul containment room where he sets up another analysis of his data. Hoping this time the system wouldn't shit all over the truth of what is going on with the new serifim formula. Sans also places two serifim syringes into two of the wires that hold his life support to see if it would trigger a reaction. "Here goes nothing." Sans says as he starts up the machine, he walks in and the water flows through the chamber as the life support is connected to his magic and the needles are pressed into his bones. The process feels extremely natural at first but then Sans starts to lose conscious too fast.

He had set the system so that him and Gaster would only lose conscious when a main scan was over, but he felt drowsy a lot quicker... Something was going wrong... out of instinct he tried to use his powers he had just gained to flick the analysis machine off but his powers leeched and he flicked the switch back and forth. A surreal sensation overcome him as he shut his eyes. He felt both of his eyes grow lighter and his bone skin become weaker, he let out an inaudible scream of terror as he felt light dissipate around him and explode in the next. The machine finally shut down as he blacked out...

He was no longer part of the machine... The lights shut off as the whole room went into blackness through his vision. The last thing he saw on the screen was that a slight overdose was created... The monster was trying to get out...


	6. Don't blink...

Sans woke with a start, the whole room was drenched, the switch was pulled in the right direction and the syringes were empty. However Sans felt like his stomach was in knots.

He then rubs his eyes and looks around to see the transfer was complete before that image was ripped from his mind and he shot to another part of the room. "What the." Sans didn't have time to ask what was going on as he zipped round the room again "What's happening to me." He shakes his head and finally gets control of himself before zipping across the room for a third time. He looks at the computer whilst trying to control his powers and finds out something went horrible wrong. It appears that his overdose went to a different power outlet when he shut down the computer, he's lost a bunch of his HP and looking at his brain data he's lost the ability to increase his attack power. In fact the exact place the Serifim went to was the blue soul powers. He can now somewhat teleport across space. 

His mind is still feeling fuzzy as he keeps on getting blurry images of events that he doesn't recognise, as well as events that are long gone. "Damn it Sans, pull it together." He finally gets control of his powers and walks over to his lab clothes, they are soaking wet and need changing. So he walks along the corridor to find Gaster. "Looks like he hit the canvas at home while whatever happened to me was going on." Sans thinks about how he can get to his home without being seen and suddenly teleports back to the damp and dark room of the soul containment chamber. He has an idea and pulls the souls out of the glass cases, he focuses his powers to the room he and Gaster was in. And in the blink of an eye he is in the room. "Woah, definitely a change now." He says to himself as he puts the souls back in the cases. As he puts the blue soul back in it's case it starts to glow. "What?" Sans' pupils shrink as he runs to a mirror and looks at his reflection. Both his pupils are now radiating a feint blue. 

~ You are filled with Integrity

"Oh my god. It worked, the Serifim theory has actually worked... Eh I'm sure I'll be fine for now." Grabbing his other equipment and drying himself off he focuses his powers once again. This time trying to reach his room. But he falls just short and ends up in Gaster's room. "Shit, hey G." Gaster turns round in shock, there was his son lying with a towel round himself and nothing else. Assumed drenched from god knows what and absent for who knows how long.

"Sans are you alright? oh for god sake turn around!" Sans gets up and gives Gaster a slightly pissed off stare. "Talk about caring for your son, did you not come back downstairs to find me?" "No" Gaster replies as if his sons response is absurd "I was busy, Jesus you're a mess. Look theres some spare clothes in your room, go and get them!" Sans hurries out of the room, dashes up the stairs and heads right to his room. Heading inside, he forgot to clean his room again today. "I can leave it till later." He finds a white shirt and a blue jacket, as well as some black shorts and blue slippers. "Eh no one cared for fashion sense anyways." He starts getting changed and hears a knocking on the door, "Sans are you coming to have a game of chess, you could do with a bit of mental orientation after what on earth just happened." "Yeah yeah, I'll be there in a minute." He says after putting his jacket on. He checks himself in the mirror giving a slight smirk. "Heh, not bad actually." He then exits and heads to Gasters rooms where his Father set up a game of chess and has already made the first move. "Ready"

"Yep" Sans says as he makes his move next. "Here we go."


	7. The game

"Check" ... Sans and Gaster are someway through their little game of chess, it helped them to understand how the Great War was played out. Whilst both sides ended up at a stalemate, there was still a loss on each side, with monsters being trapped underground and the cost of human life at an enormous toll.

One day they hope to end this pitiful game and beat the other side, reclaiming their land. Gaster moves his pawn on top of Sans' rook and the game is back to normal.

"Do you think they'll ever consider this folly war to be a waste of time." Sans' questions as he plans his next movement. "Of course not, Asgore has never been one to look ahead to the humans thoughts. Besides, what makes you think we should stop?" Sans uses his powers to move the next piece "Why should we have to do all this painstakingly difficult work, It seems like a list of rash actions." Gaster looks bewildered that his son should suggest this action "Sans I told you before, check, one day you'll have to learn to live with your choices. It seems the king is well in that position right now."

Sans still looks slightly annoyed. "(Sigh) Listen G. I understand you're trying to find a way out of here, but maybe that's not what we should be focusing on, check, didn't asgore say that he could get seven souls." Gaster drinks his coffee and plans his next move. "Sans my work has to be done and I've expected you to help me throughout this, didn't you say you want to get out of this place, Check." 

"I don't know, maybe you're just not seeing the bigger picture yet. After looking at those quantum physics details my research was right. Eventually someone is going to fall down here with the ability of a red soul. And only they will have the choice of whether we live or die." Gaster looks at Sans with a face of disbelief "You don't seriously believe all those rumours in the ruins too?"

"I'm willing to put my money on it. If you can't see it then I won't judge you for it... Because right now, all I see. Is a room with no light, and my DETERMINATION fluctuating until it comes to a resolve... Guess we'll have to see what that black room is then won't we... Checkmate!" 

Sans finishes his speech and teleports away, gaster looks down at the game seeing his son has won and looks up to see he disappeared. 

"Thought something was wrong with him, he's growing faster in power than I thought. I wonder if..."

Sans headed over to the kitchen to grab a drink and papyrus was sitting on the sofa watching TV "Hey bro, watching a royal guard procession?" Papyrus replies with his eyes still lightly fixed on the TV "Yeah, man undone is so cool. I hope someday I'll get to be in the royal guard." Sans heads over to the sofa and sits down himself "Yeah well I don't see what the fuss is all about." Papyrus has a slight scowl on his face but quickly lets it slide. "Hey brother are you alright, father said you're acting strange lately." "Sounds like his "funny" bones broken, heheheh." Papyrus chuckles but still is annoyed by his brothers light hearted nature.

"SANS!" "Heheh, come on you're smiling. Anyways don't worry about me, I'm fine. Just this stuff that I've been doing with our dad has taken a real toll on me."  
"Just be careful alright." Papyrus says with evident worry in his voice "Hyeah, I will." Sans says rubbing his brothers head.

That evening the two of them sat down and watched TV until Papyrus had fallen asleep, sans picked him up, grunting a little bit at his weight. And took him upstairs to his room. Put him down on the bed and tucked him in. "Night bro." He says as he walks away turning off the bedroom light as he leaves.

Suddenly he sees his father at the bottom of the stairs.

"Sans, I did it. I know how to mutate our souls powers


	8. Eruption of a Soul

"G you're making a mistake here." Sans says as he tries to get Gaster's soul hands off of him. The two of them are walking over to an analysis machine that Gaster was working on before, Sans is suddenly thrown in and gaster uses his magic to seal all of the life support systems on him. "I'm going to inject your body with as much Serifim as possible. The soul is able to withstand only a certain amount of Serifim at a time, but if I push it past that your body will mutate."

Sans speaks with effort as he struggles to try and free himself, but Gasters hands have him held their. "Gaster if I'm given to much of that stuff I might die, all the work that we've done is going to go down the drain. Just think about this..." Sans couldn't finish his sentence as he feels an anaesthetic inject into his skull and multiple syringes arch towards his body, plunging into his bones. Two on his arms, three at his head, two on his legs, and finally, four on his left hand. Where his knuckles would be.

"Sorry son, it's the only way. I, am, DETERMINED."

Gaster leaves his son to suffer in the analysis machine while he goes to work on the core... Strangled noises are heard from Sans as the serifim slowly keeps on flowing into his blood stream. He passes out...

After 20 minutes he wakes up in excruciating pain. He flinches as he feels his eyes start to glow harsher than what they did in the mirror, suddenly one of them bursts and his whole body reacts. Things around the lab begin to shake and the Gaster Blasters begin to come alive. Sans opens his eyes as an explosion of blue flame erupts from his left eye and he screams in anger and pain. The analysis machine breaks apart as the syringes burst and the serifim keeps on digging into his digits. He breaks free of his prison still screaming in pain and falls to his knees. He gets up with a bit of a struggle, voices of the past and future are ringing in his head. He feels his memories and possible futures flash before him at an alarming rate. He heads to a mirror to look at himself, a blue, fiery eye is blazing in his left eye socket. He can't get rid of it as the serifim has taken full control of his powers. If the last overdose wasn't bad. This had worked.

He was mutated.

The monster was free.

The Gaster blasters snap from their restraints and fly over towards him, he finds he can spawn them in and out of existence. All of his thoughts fixate to one person. 

Gaster.

He was going to bleed for what he had created of his Son, Sans searches his soul and finds his Father in the core room, doing tests on chambers of determination. He was planning to use the determination to power the core. If he did that the core would erupt no doubt.  
Sans blinked out of existence and released his anger as he arrived at the entrance of the core. He started to make his way through the core.  
The blue soul back at the lab was glowing brightly  
"...Check... Now. It's my move!"  



	9. Stalemate?

Sans takes the elevator to the top of the core, Gaster is testing his powers on the core and they are amplifying dangerously. It seems that a persons powers would increase with this much magic surrounding them. 

He turns round with his focus knocked away from him to see the elevator rise up in a puff of smoke, Something was inside the lift. Without warning a blue light erupted and a violent roar of anger was heard as Sans lunged towards Gaster sending them tumbling into a computer room. The magic pool of the core was waiting to swallow them up as Gaster threw his son of him. Sans reacted immediately and threw bone attacks at his father. Gaster was able to counter them and attack, but Sans used his blue magic to grab the bones and break them. 

"What have you DONE TO ME!!!" Sans says as his blue eye is shining like a beacon in those black sockets. "Hahaha, what do you think you're doing son. We succeeded, you're now more powerful than I could ever hoped to be. You should thank me." Sans looks angered "I don't want any recognition, I'm a freak now! Your lust for power has turned me into a monster." Gaster looks on amused, his memories of his son have gone and his eye to the future blinding him. "If it's a fight you want Sans then have at it, I'm not stopping you." Gaster tries to grab him with one of his magic hands, but Sans vanishes. "What the-" "Who says I wanted to fight you." Sans says, his father back to back with him. "You brought this upon yourself gaster!" Gaster suddenly feels weightless as he sees two skulls appear behind sans, he is lifted off the ground as the skulls vanish. "I'm not here to fight... I'm here to make you feel pain, for as much pain I suffered from those syringes." Gaster is then thrown to the ground held down as if gravity is forcing him down. He jumps up just to avoid a line of bones and then the skulls flashed into view charging white hot, blue energy balls, he runs for cover as the skulls erupt and fire directly at him in large laser attacks.

Gaster comes out of the attack only injured slightly but he notices his health has dropped more than he expected. "How's that for karmic retribution?" Gaster smirks ready to fight. "Clever, but they won't help you enough." Gaster uses a hand and turns it red firing a red laser beam at Sans. The skeleton avoids it and charges at Gaster jumping over the bone attacks whilst Gaster tries to force him down further with his blue attack.

"Oh I beg to differ." Sans says as he teleports again behind gaster kicking him in the leg. Gaster yells in pain and grabs Sans by the hand smashing his head on the ground. Sans feels his head crash onto the stone floor but gets up, still in pain. and uses his blue attack to throw gaster across towards the balcony. He follows after him teleporting along the way.

~Gaster feels his sins crawling on his back. 

The fight between the two lasted a while until Sans let off a wave of gaster blasters, by mistake one breaks into a determination container and the two of them are blinding in the explosion. Sans wakes to find his father on the ground choking in pain as red liquid drains into his wounds. His father takes one look at him still trying to combat the pain and then falls off the balcony into the core. Sans watches as he is ripped from the world and is scattered into a million pieces.

Sans feels pain as well as the determination liquid starts leaking into his scars. He struggles in fear and anger and pain. All these bottled up emotions conflicting in his fight to stay alive with this determination damaging his body. He sees a golden star and uses his powers to pull it towards him. Grabbing it he is blinded by the light and the determination is absorbed by the star. He passes out.


	10. Mutation

~The darkness is taking your soul...... But you refused...

Sans wakes up gasping for air, his shoulders shuddering as he lies on the ground, all of the pain he experienced was sealed away. He looks to his side to find the golden star still in his hand.

It was filled with the determination he got infected by, all of the pain he felt moments ago was trapped inside this Star. He feels his face to find a scar wrapped across his right eye. His clothing is torn and the place is surrounded in electrical disturbances and flames that lick the walls of the corridors below him. His head falls inline with his back as he looks up at the ceiling, his body goes limp as he drifts between life and death.

Four guards of the core crash in and find him lying on the floor. No trace of his father anywhere. “Holy shit... You two pick him up and get him to Gaster and Dr Alphys, you come with me. A knight knight and a Madjick pick up Sans’ limp body as he is carried out of the core and is rushed to New Home urgently...

“This is all just a bad dream... and you’re never waking up.”

Sans opens his eyes to see Asgore checking his bed and alphys looking over life data. “Oh Sans, good to see you’re still in one piece. Someone must really care about you.” He says smiling at the skeleton lying on a recovery bed. Sans looks on to see Alphys walking over to him. “Alphys, heheheh. You look worried about something.” “You should be too, after what you’ve been through you should be dead.” Alphys scans Sans to find anything unusual going on in his bloodstream but to no avail she prepares to leave “Hey Alphys, I couldn’t stop it. He’s gone.” 

Knowing Sans is talking about Gaster, Alphys nods sadly “I know. He’ll be alright.” She leaves Sans on the bed.

She comes back a few hours later. “What’s the damage doc?” Alphys looks at her notes with a reluctance to believe the truth in this instance. “Medically you seem fine. The Serifim seems to be healing your wounds and your powers are strong and still working. But there are two issues... because of the Serifim injection you seem to have mentally suffered a horrific mutation. You have abilities that are unnatural to monster... Sans what I’m basically trying to say is you’re part human now... take a minute I know this may be a shock to you.”

(“What she was saying made sense, I could see timelines like they were clear cut to me and had determination in my bloodstream to back this evidence up.”)

“And the other issue.” Alphys sighed “you’re not gonna like this one, it appears that the determination you absorbed but countered with the star has had a trade off, while you have these abilities your stats are extremely conflicted. You are 1 in nearly every data check, you will die with a mere punch. That is if the punch is inflicted correctly. You may be able to reduce damage by increasing your speed thanks to your new tricks. But just be careful... that’s all I’ve got. Sorry.”

(“Bottom of the barrel, bullshit. Where my life went wrong was at this particular moment. And the thing is, I didn’t just have to powers to break spacetime. I had the powers to break everything...”)


	11. I created a monster...

The walk back to snowdin was rough for Sans. He passed quite a few of monsters on his way, but he was almost unrecognisable. Some asked him if he was alright to which he nodded with a bleak smile, while others started walking away. Some just looked at him in surprise. He was destroyed on the outside. But there was one person who would no doubt care about him whether he looked like hell or not.

He steps into his house to find his brother watching TV, he gives him his best grin possible but to no avail, his brother looked heartbroken that Sans was put through so much pain. "Brother, are you alright." He says getting up from the sofa and walking towards him. Sans kneels down and hugs his little brother who appeared to be crying, Sans holds back his own tears, but he can't help but sniffle through his nose as he suppresses his sadness. "Yeah, I'm alright bro. Sans is here." Papyrus lets go and looks up at him with evident sadness on his face too. "I miss our father Sans, why did he have to do this to you." Sans shakes his head. "I don't know pap... I don't know."

The hours pass as the two of them watch TV and try to get through the day. Sans eventually heads over to Grillby's while his brother was having his supper. The place didn't have too many customers this evening which he was grateful for. "Rough night Sans?" Grillby says to him as he sits by the bar. "You have no idea buddy, get me a ketchup." Grillby walks over to the condiments area, he knew that Sans only had ketchup as a drink when something was off, otherwise he would just have a beer or water. "Listen Sans, it can't be that bad can it, it's only a couple scars an- OH, my, god!" Grillby says interrupting his own sentence as Sans pulls his hood off and lets his left eye light up in flame. "You like what you see?" "No... God no. Jesus you look like a candle just took a shit on one of your pupils." Sans gets rid of his blue eye promptly "Thanks for the motivation... Oh and don't even try punching me, because my body is now meant to be weaker. Than a fucking whimsum!" Grillby sighs in knowing. "That's not good. Listen Sans i don't really know what to do for you at this point since I guess you really are on the wrong side of the world. But just be careful out there alright. Besides i've got your back."

Sans looks up at grill by with a slight smirk "Thanks, cheers." Sans downs his drink and pulls out extra money "Drinks are on me. These boys are thirsty!" Sans says while heading out, the monsters there give him a cheer as grillby looks on chuckling to himself...

The skeleton heads round his house down to the lab. All of these dark memories still hiding in plain sight. He walks through the dimly lit corridors remembering all the experiences he had with Gaster. The fights, the drama, the controversy, the friendship, the fun, the comradery... He notices a blue tear trace his eye as he wipes it away. 

He looks at a cylindrical machine that was covered by a cloth. He pulls the cloth off with his blue magic and reads the note on it.  
~IN CASE OF EMERGENCY FROM DEATH, Sans if you are reading this. Then most likely I am dead... I may not be in the right mind to come back yet as I will have only been gone for a mere day or two. but when the time is right, you will know. I wish you the best and, please take care of papyrus. Your Father, Teacher, and more importantly your Friend.  
W.D.Gaster  
~G 

He looks at the machine knowing it's purpose. "When the time is right G. When the time is right." He walks away and turns off the lights in the laboratory. He walks back outside and indoors to his home. "Alright time for bed you." Papyrus notices Sans come in and sigh "Alright." the two of them walk upstairs and papyrus jumps into bed. Sans turns off the light and waits outside. He hesitates for a moment but walks back in door stroking his head as Papyrus falls asleep. "Sleep well bro." He says as he walks back into the hallway and shuts the door, he heads downstairs and lies on the couch. Eventually falling asleep himself... However, the peace didn't last...


	12. ...A hell within my head

Sans walked through the subconscious hallways of the lab as he witnessed a memory of him and gaster at work, developing the analysis machine he was tortured in, developing the gaster blasters he would use to fight against his former friend. He watches his former self at work developing the power outlets and how they would format in the monster world. He soon feels his fire leech from his eyes, trying to take control of his memory. He tries to stop it by covering his eye with his hand but it just moves around it. His memory self uses his blue power to remove the flames and puts a hand on his teeth (or lips. whatever) telling him to keep quiet. "Ssshhhhh." "You alright Sans?" Gaster asks and Sans stops "Yeah I'm good, as you were saying?" The memory plays out exactly as he expected it. and he follows his former self through to the soul containment room. "Hey, wait. Can you tell me what's going on?" His memory enters the analysis machine and fires it up just as he remembered. "Please, I need some answers. Why am I here." 

"Hey buddy." The memory sans speaks to him, Sans doesn't even realise his flame is leeching from his eye again. "You gotta give me a break, I'm doing the best I can for you. You have to figure out what this all means... But I must say if you keep all this going... Y o u a r e r e a l l y n o t g o n n a l i k e w h a t h a p p e n s n e x t . . ."

That is all he hears from his former self as his eye catches the lever and pulls it back and forth. He is blinded from his own powers and he screws his eyes shut at the sight of him being almost stabbed by the machine.

He wakes up on the couch of his home. "Woah! what was that... What did he mean by if I keep this going. Keep what going, he couldn't have meant... Oh my god, he's trying to come back too early... I need to talk to Alphys and Asgore. Papyrus!" He shouts for his brother as his brother opens the door "Brother are you ok." Sans nods and motions him to come downstairs. "Yeah, come on we need to go see Alphys and Asgore, now." Papyrus looks confused as to how they'll get there now. "But it's late, how are we going to get there quick enough?" Sans smirks at his brother grabbing his hand. "Don't worry, I've got a shortcut."

Sans found Alphys and Asgore and explained everything too them. The dream, the experiments, his powers. The evidence that Gaster is trying to prematurely return. "Are you absolutely sure Sans?" Sans nods "Of course I'm sure, otherwise I wouldn't be here at this time of night." Papyrus sits beside him as the four of them are in new home having a drink and discussing the matter. "Well what should we do brother?" Alphys looks over her notes on the matter and finds a reasonable solution. "I know what we should do, papyrus do you mind leaving for a moment." Papyrus nods and heads into another room. "Alright, if you're absolutely sure Sans, we need to erase the past. At least as far so that no one will truly understand the matter. Asgore, I need you to go to the core, I will meet you there and we must shut it down until we can stop Gaster from return immediately. Sans, you know what to do." Sans nods. "Everything must go. Data, Machines, blueprints. Anything we can find that will give other monsters ideas about what we've done... Then it's settled, Alphys let's go." Alphys nods as the two of them teleport to the laboratory to destroy what Sans and Gaster created.


	13. ERASE

Sans found himself in the Laboratory with Alphys smashing up any research that needed to be removed. Alphys told him that some blueprints may be salvaged for future use of hers. And that Sans personal items such as the Matter chamber could be stored away after the whole place is sealed off properly. But until then he was tearing up blueprints and removing archives of anything he had done. And anything his father did.

He hears a voice in the room "I see you're starting to realise the consequences huh?" Sans kept at work but still responded to his figure from the past. He was pretty much like a ghost being ethereal. But Sans knew it was his own power generating this apparition. "Looks so... How come you're still here." The ghostly version of Sans shrugged and starting cleaning out the place with blue magic and bones "Figured you would still need some help controlling your powers, but you'll learn to minimise this." The ghostly figure looks at a bone that Sans was holding. "Mind if I borrow that." Sans nods and chucks it towards him. "I've been wanting to do this for quite a while now." With one swift motion the Bone enlarges into a sledgehammer shape and he smashes the analysis machine with a cry of DETERMINATION. He then blows the rest of the chemicals and glass and components to smithereens with a gaster blaster.

"I don't get it. How exactly does my power link with you." Sans asks as he watches the ghostly figure continue to go about his business tearing up folders. The apparition pulls out Sans soul to show it's still grey, but has a hint of blue. "See how your soul is grey. Well it seems that the Serifim formula was set to be modified in accordance to two soul types; Determination, and Integrity... If you look closely you'll see a blue point in the centre of the soul... When I'm inside the soul it turns fully blue. Allowing you to fully control your powers. But when using certain powers like Teleportation it causes a large amount of matter to rupture, causing your soul to drain of it's blue power. And in turn creating an after image of me."

Sans seems to understand all of this like he was born with these powers. "Of course you're still moving faster than light, but this means you can control your attacks properly. In fact it reduces IF. What's IF, it's an acronym. It stands for Instinct frames. A way of measuring a souls ability, or inability to react to moves. This is triggered by KR, or Karmic Retribution. When an opponent has enough KR their IF decreases. Allowing multiple attacks to be made at once."

"So when I'm attacking someone, with these powers I'm essentially able to deal 15HP in a 1HP attack?" His ghostly figure nods. "You're a lot stronger than you think Sans, and you'll have Karmic Retribution too." 

The two of them finish their work in the Laboratory. "Alright that's everything, Alphys is taking the souls to the king where they are safe and my personal stuff is in the entrance to the lab." The ghostly figure walks up to Sans and grins "It's not over yet buddy, there is still one more thing left to be done." Sans looks confused, but then promptly guesses what is going on. "Wait, so let me get this straight. If the core is made from Monster magic. Monster magic that stems from part of our refracted souls. Then that means determination is held within the core-" His ghostly figure interrupts "-And do you really know what determination causes." Sans' eyes shrink in realisation "Rips in spacetime... He's here." The ghostly figure chuckles knowing his work is almost done. "You know where to go... Good luck, partner." He disappears into Sans' soul and Sans' left eye sparks up once again. He focuses his teleportation to waterfall where civilians are confused about a door in the wall. They all stand back as Sans walks over to the door, either in fear or hope they all watch as his hand grabs the handle of the door and turns it open.

~You don't remember a door like this being here before. However you stay DETERMINED!"


	14. Dark, darker, yet darker.

Sans enters the dark room through the mysterious door. He remembers talking to his father about a dark room. The door slams shut behind him as he turns to a light in the room... Only the light was covered by a perfect shadow encasing it's structure.

Sans felt dark creatures on the floor. flowing through his hands as if trying to trick him into grabbing their form and crawling on his back as if they wanted to drag him down.

"Beware of the man who speaks in hands." He feels a boney appendage grab onto his hand and start to fade. Darker and Darker, it would never let go as Sans tried to shake it off while another hand also latched into his other hands. He looks at the light in front of him. It was still getting dark, despite being as dark as possible. It would never stop becoming dark, darker. Yet Darker as he starred at his hands with frustration. The creatures eventually get flung off and fly into the light.

~W.D G45t3r 4850r83d th3 d4rkn3ss...

Sans flinches as his physical matter is sent outside of the room and back into the corridor where the other monsters were. The light starts moving through the walls and forms into a cloaked figure. Gaster had returned. His entire body was connected to the floor in a cape like figure and his head had two scars from his eyes. They looked like they were going to split but resisted breaking open. The Two appendages hand become hands separated from his body in a Dark blue and Red color. 

"G-Gaster... Is that you." Sans spoke as the figure stood silent. All the while a light static noise was in Sans' mind. "Finally, i've been set free from void... But i never thought i would be released by your magic..." The figure chuckled as he looked up to see his son standing above him. He grins in a slightly disturbing smile. "You're looking good Sans. Still hanging onto this mortal coil i see." Sans stood there bewildered by this sight. He was literally talking to a person that should be dead. "What is going on Dad?" He asks as the figure moves around the corridors, inspecting the rivers flowing around him. "We succeeded Sans. We both gained power that would rival even the likes of the strongest monsters in the underground... When i left you, i was but naive. I expected to easily overcome your power and show you that i was right." 

Sans rubs his eyes down his face "Well that didn't turn out too well for either of us now did it." Gaster touches an echo flower, his body matter caressing it with care as it slowly dies. "But something is wrong with me... I should be dead, but i'm not... It's funny because when i entered the void. They didn't expect me to weak, they thought i was you." Gaster chuckles in a strained sort of way. "They? The souls of the dead?" Gaster nods "My, my. You do catch on don't you." Sans feels his soul disperse and his temporary spirit standing beside him. "I figured it out G. I knew you were planning to come back. It was only a matter of time before I (present sans) caught on to why the world was dying... You're an anomaly." Gaster looks at them both. "I told you a long time ago. There were consequences that come with choices... But consequences are made to be broken... I started out my work, and i intend to finish. But i can't do it like this... Your soul, it can bring me back. It can make me whole..." Sans feels his soul become warm again as his ghostly counterpart disappeared. Sans then sees five other hands surround Gaster, forming the colours of human souls. The hands turn red and charge up a ball of energy. "I just have to kill you once right!" Gaster releases the ball of energy and it explodes swallowing up Sans in the blast.

~Gaster is trying to take your Soul......


	15. Game over

~...But it refused

The red ball of white hot energy turns blue and explodes with Sans destroying it. His left eye a-blaze with power. “Sorry G. But you’re right, I’ve lived with my choices, and now it's time for you to do the same... you’re gonna have to try a little harder than that!”

Gaster and Sans fight for an incredibly lengthy amount of time as they both try to gain the upper hand. Whilst Gaster has gained a large amount of abilities and strength from the void. Sans had become more formidable and cunning. Outsmarting Gaster as he destroyed each of the seven hands he held by his side. Gaster was left on the floor in dispair.

“You don’t know how this feels to be abandoned and trapped in pain.” Sans shakes his head as he walks to his father. “That’s a perfect description of what you put me through in that lab.” Gaster sighs “You won’t stop me. I will come back... using any means neccisary!” Gaster uses the black creatures to attack Sans...

But the attack never strikes Sans as he stares at his Son. He has two bones struck through his chest as he begin to crumble and die. Being sent back to the void, trapped as a shadow. Observing the world below him.

“Sorry Dad, but you made a miscalculation... checkmate!” Sans says as he watches his fathers eyes dim and he turns to dust that eventually disappears.

~You knew the bad time was over

“I guess that’s it then huh.” His counterpart says to him. Sans nods as he walks home. “What about you. What are you gonna do now that he’s gone?” Sans asks “I think I might take a break, I deserve one after all the rib tickling antics I’ve been through.” Sans chuckles “heheh good one... well I guess I’ll see you around.” He feels his counterpart smiling. “Yeah, be seeing you buddy.” His soul returns to his Blue state and never turns back. He went back to his home and relaxed. Knowing that it was all just a bad dream. And he had finally woken up.

“Thats some story” Frisk says as they both stare up at the stars. They were outside watching the night sky as Sans was finishing his story. “Hyeah it was pretty rough back then. But I’m glad things have changed... Anyways you better get to bed.” Frisk nodded “alright, night Sans.” Sans watched as she left.

(“She’s done a lot for us huh.”)

Sans feels Gasters thoughts travel inside him

(“Yes she has... It seems that we have all been given the chance to live with our choices after all... Goodnight Son.”) 

(“Goodnight Dad.”)

Sans finishes his telepathic conversation and heads to the door. Taking one last look at the stars outside.

“Goodnight partner.” He says as he walks through the door of the past and continues through his present. Waiting for what lies ahead in the future.


End file.
